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Alfredo Pasquarello

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Related publications (226)

Comparison of vacancy and antisite defects in GaAs and InGaAs through hybrid functionals

The formation energies and charge transition levels of vacancy and antisite defects in GaAs and In0.5Ga0.5As are calculated through hybrid density functionals. In As-rich conditions, the As antisite is the most stable defect in both GaAs and InGaAs, except ...

2012

Band-edge problem in the theoretical determination of defect energy levels: The O vacancy in ZnO as a benchmark case

Alfredo Pasquarello, Audrius Alkauskas

Calculations of formation energies and charge transition levels of defects routinely rely on density functional theory (DFT) for describing the electronic structure. Since bulk band gaps of semiconductors and insulators are not well described in semilocal ...

2011

Advanced Calculations for Defects in Materials: Electronic Structure Methods

Alfredo Pasquarello, Audrius Alkauskas

This book investigates the possible ways of improvement by applying more sophisticated electronic structure methods as well as corrections and alternatives to the supercell model. In particular, the merits of hybrid and screened functionals, as well as of ...

Wiley-VCH2011

Charge Trapping in Substoichiometric Germanium Oxide

Alfredo Pasquarello, Peter Broqvist, Jan Felix Binder

Electron and hole trapping in substoichiometric germanium oxides are investigated through the use of hybrid density functionals. We consider disordered model structures generated by Monte-Carlo bond switching and by ab initio molecular dynamics (MD). The M ...

2011

Band offsets at Ge/GeO2 interfaces: Effect of different interfacial bonding patterns

Alfredo Pasquarello, Peter Broqvist, Jan Felix Binder

Using hybrid density functional calculations, we investigate possible origins for the large variation of band offsets measured at Ge/GeO2 interfaces. We consider atomistic model interfaces with both amorphous and crystalline oxides, in which the bond densi ...

Elsevier2011

Structural Composition of First-Neighbor Shells in GeSe2 and GeSe4 Glasses from a First-Principles Analysis of NMR Chemical Shifts

Carlo Massobrio, Alfredo Pasquarello, Mikhail Kibalchenko

Isotropic chemical shifts and quadrupole coupling parameters of Se-77 and Ge-73 nuclei in GeSe2 and GeSe4 glasses are determined through density-functional NMR calculations on amorphous model structures generated by ab initio molecular dynamics. The compar ...

American Chemical Society2011

Assessing the accuracy of hybrid functionals in the determination of defect levels: Application to the As antisite in GaAs

Alfredo Pasquarello, Hannu-Pekka Komsa

The accuracy of nonscreened and screened hybrid functionals for the calculation of defect levels within the band gap is assessed for the As antisite in GaAs, the nature of which is well characterized experimentally. A set of functionals differing by the fr ...

2011

Vibrational properties of vitreous GeSe2 with the Becke-Lee-Yang-Parr density functional

Carlo Massobrio, Alfredo Pasquarello, Luigi Giacomazzi

The vibrational properties of vitreous GeSe2 are studied within the Becke-Lee-Yang-Parr (BLYP) generalized gradient approximation to density functional theory. For this purpose, we consider two models. The first one is derived from a chemically ordered net ...

2011

Charge transition levels of carbon-, oxygen-, and hydrogen-related defects at the SiC/SiO2 interface through hybrid functionals

Alfredo Pasquarello, Fabien Devynck, Peter Broqvist, Audrius Alkauskas

We calculate charge transition levels of various defects at the SiC/SiO2 interface within a scheme based on hybrid density functionals, which accurately reproduce the involved band gaps and band offsets. The defect levels are first evaluated in bulk models ...

2011

Identification of defect levels at InxGa1-xAs/oxide interfaces through hybrid functionals

Alfredo Pasquarello, Hannu-Pekka Komsa

Hybrid density functional calculations and atomistic models are used to study point defects in III-V compounds. We first study dangling-bonds in InxGa1-xAs. In GaAs, the cation dangling-bond levels are found in the upper part of the band gap, but they are ...

Elsevier2011

Band offsets at the Ge/GeO2 interface through hybrid density functionals (vol 94, 141911, 2009)

Alfredo Pasquarello, Peter Broqvist, Jan Felix Binder

2011

Electron density of states at Ge/oxide interfaces due to GeOx formation

Alfredo Pasquarello, Peter Broqvist, Jan Felix Binder

An atomistic model of substoichiometric germanium oxide is generated through ab initio molecular dynamics. The resulting structure shows a predominance of threefold coordinated Ge and O atoms. We also generate substoichiometric models through bond-switchin ...

Elsevier2011

Defect levels of carbon-related defects at the SiC/SiO2 interface from hybrid functionals

Alfredo Pasquarello, Fabien Devynck, Peter Broqvist, Audrius Alkauskas

We investigate carbon single-atom and pair defects at the SiC/SiO2 interface as candidate defects for the density of defect states in the SiC band gap. In order to accurately describe the electronic defect levels with respect to the SiC band edges, we use ...

2011

Defect levels through hybrid density functionals: Insights and applications

Alfredo Pasquarello, Peter Broqvist, Audrius Alkauskas

Hybrid density functional calculations applied to defect charge transition levels are explored in the attempt to overcome the band-gap problem of semilocal density functionals. Charge transition levels of a large set of point defects calculated with semilo ...

2011

Charge transition levels of nitrogen dangling bonds at Si/SiO2 interfaces: A first-principles study

Alfredo Pasquarello, Philipp Dahinden, Peter Broqvist

The defect levels of the nitrogen dangling bond at the Si/SiO2 interface are determined through a density-functional approach. The composition grading at the interface is modeled through crystalline and amorphous models of stoichiometric SiO2, nitrided SiO ...

2010

Alignment of defect energy levels at the Si-SIO2 interface from hybrid density functional calculations

Alfredo Pasquarello, Peter Broqvist, Audrius Alkauskas

2010

Formation of substoichiometric GeOx at the Ge-HfO2 interface

Alfredo Pasquarello, Peter Broqvist, Jan Felix Binder

The stability of oxygen vacancies across the Ge-HfO2 interface is studied through semilocal and hybrid density-functional calculations. On the semiconductor side, the formation energies are obtained for substoichiometric GeOx of varying x through the use o ...

American Institute of Physics2010

Electronic and structural properties at Ge/GeO2 interfaces: A density-functional investigation

Alfredo Pasquarello, Peter Broqvist, Jan Felix Binder

The electronic and structural properties at the Ge/GeO2 interface are addressed through a density-functional simulation scheme, which includes the use of hybrid functionals for achieving defect levels and band gaps comparable to experiment. The present wor ...

Electrochemical Society Inc.2010

Metal catalyst in CVD growth of carbon nanotubes: role of chemical composition

Alfredo Pasquarello, Oleg Yazyev

Using first principles methods, we systematically study the crucial steps of CVD growth of CNTs, the binding and the diffusion of the carbon feedstock as well as the nucleation of CNTs. Late transition (Ni, Pd, Pt) and coinage (Cu, Ag, Au) metal catalysts ...

American Institute of Physics2010

First-principles investigation of the relation between structural and NMR parameters in vitreous GeO2

Alfredo Pasquarello, Mikhail Kibalchenko

NMR parameters of Ge-73 and O-17 in vitreous GeO2 and quartz GeO2, including the isotropic shifts, the quadrupole coupling constants C-Q, and the electric-field-gradient asymmetry parameters., are determined through density functional calculations. Clear c ...

2010

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